There exists serial-type image forming apparatuses, in which an inkjet print head mounted on a carriage moves relative to and ejects recording fluid or ink from a nozzle, which is formed on the inkjet print head, toward a recording medium so as to form an image on a surface of the recording medium including a recording sheet, transfer material or any kind of recording material. While the recording sheet, for example, is conveyed at predetermined intervals according to a recording width of the recording sheet, the carriage reciprocally moves in a direction perpendicular to the direction to which the recording sheet is conveyed and the inkjet print head ejects liquid droplets of ink from the nozzle toward the recording sheet. By repeating the conveyance of the recording sheet and the travel of the carriage, an image may be formed or printed on the recording sheet.
Some inkjet print heads are prone to defects due to viscosity-increased ink. To maintain and refresh the ability and condition of the inkjet print heads and clean the nozzles formed on the inkjet print heads, a maintenance unit is required to correct the defects.
The maintenance unit generally includes a capping member for tightly covering a nozzle mounted surface of the inkjet print head and preventing an increase of viscosity of ink around a nozzle formed on the inkjet print head, and another capping member for removing and purging the viscosity-increased ink from the nozzle. These capping members may be formed in one capping member having both of a moisturizing function and a purging function. The maintenance unit further includes a wiping member, such as a wiping blade, a cleaning blade, a wiper, a blade member, a blade or so forth, for wiping and removing the ink adhered to the nozzle mounted surface, and a dummy ejection receiver for purged ink that is not used for image forming or becomes defective.
When the carriage is moved while the capping member covers the nozzle mounted surface, the position of the capping member may change and become unstable. The unstable capping condition may increase the speed of developing viscose ink to clog the nozzle, which can cause ink ejection defect.
Further, the capping member may physically damage the sealing portion of the nozzle mounted surface, which can cause a suction defect due to a leakage of ink from the nozzle.
To avoid the above-described conditions, a carriage locking member may be included in an image forming apparatus so as to lock the carriage having the inkjet print head thereon to a predetermined position. With the above-described condition, the inkjet print head can reliably be kept to the predetermined position when the defective or unused ink is removed from the recording head while capping the nozzle mounted surface of the inkjet print head.
Further, to downsize the maintenance unit, the image forming apparatus in the background art may use a common driving source for the carriage locking member, the wiping member, and a suction pump for removing ink from the nozzle.
However, since the carriage locking member and the capping member are generally not mechanically interlocked or operated at the same time, the capping member needs another driving source that is different from the driving source for the carriage locking member, wiping member and suction pump. As a result, the maintenance unit may have increased size, operational complexity, and cost.
Further, when the capping member covers the nozzle mounted surface while the carriage locking member has not properly locked the carriage, the capping member cannot cover the proper area of the nozzle mounted surface. When the carriage is moved or the recording sheet is conveyed under this condition, the capping member may come off the nozzle mounted surface, and as a result the viscosity of ink in the nozzle can increase, the increased-viscosity may clog the nozzle and deterioration in image printing quality may occur.
In addition, the movement of the carriage while the capping member covers the improper area of the nozzle mounted surface can damage the capping member and prevent the proper ink removing operation.